Juicy details – why fruit juices pose a hazard to our health

Fruit juices generally have a healthy reputation, and a lot of people see them as a decent swap for whole fruit. However, for a variety of reasons, fruit juice actually bears only a passing relationship to the from whence it came. One reason for this relates to the fact that many nutritious elements in the fruit can get left behind during the juicing process. Also, juicing makes the sugar in fruit more accessible to the body. This is important, because the sugar concentration of fruit juices is essentially the same as sugary soft drinks.

Now, I don’t think that fruit juices are in the same nutritional league as soft drinks – they do at least offer some nutritional goodies that you won’t find in a can of pop. However, their highly sugary nature does mean they might have weight-boosting potential and may pose other hazards for the body too.

In this week’s edition of the journal Pediatrics, evidence is presented that children drinking fruit juices do indeed seem to at risk of piling on the pounds [1]. The risk, in this study, seems to have been confined to those children who are already overweight or deemed at risk of becoming overweight.

One of the most plentiful sugars in fruit juice ” fructose ” is often touted as a healthier alternative to another form of sugar found in food known as sucrose. Part of this ‘healthy’ reputation is based on the fact that fructose is the predominant sugar found in fruit. Another factor said to be in fructose’s favour is that it does not cause blood sugar levels to rise in the way sucrose does. However, the reality is there is plenty of evidence suggests that fructose is every bit as damaging to the body as sucrose. Below, I’ve added a couple of pieces that explore the hazards associated with consuming ‘healthy’ fruit juice and fructose.

Observer Column – 26th September 2004

In previous columns I have been overflowing with enthusiasm for the benefits to be had from drinking water. Many individuals find that keeping fluid levels topped up can stave off feelings of fatigue and lethargy, and research has linked increased water consumption with a reduced risk of a range of conditions including heart disease and some forms of cancer. I was therefore very pleased to learn that the Government has recently recommended that school pupils be allowed to take water into the classroom. This move seems to have been triggered by British research which shows that even relatively mild dehydration may provoke headaches and irritability in children, and may cause brain power to dry up too. It seems allowing access to water during lessons could well encourage fluid thinking in our kids.

I note that another of the Government’s recent recommendations concerning liquid refreshment is for fizzy drinks in school vending machines to be replaced with fruit juice. While juices derived from fruit obviously offer better nutrition than sugar-charged or artificially-sweetened soft drinks, there are other things about them that does not whet my appetite. For instance, in the juicing a fruit a degree of its nutritional goodness (such as a good deal of its fibre and a proportion of its nutrients) get left behind. Also, most fruit juices are dehydrated, rehydrated and pasteurised prior to packaging. Overall, such processing is only likely to detract from the nutritional benefits offered by whole fruit.

Juiced fruit typically contains a blend of fructose, sucrose and glucose which, together, give it a sugar concentration that is very similar to that of regular soft drinks. Such sugariness, coupled with an acidic nature, has caused fruit juice to be cited as a risk factor for both dental decay and a wearing away of tooth enamel known as dental erosion. Once swallowed, the high sugar content of fruit juice can pose problems for the lower reaches of the gut too. Some children may be unable to absorb such a glut of sugar efficiently, which can lead to fermentation in the bowel with resultant bloating and wind. Also, excesses of sugar may draw water into the gut, precipitating diarrhoea.

Once absorbed from the gut, the sugar in fruit juice may pose other hazards by stimulating the production of insulin – a hormone which increases the production of fat in the body, while at the same time stalling our fat-burning potential. Evidence is amassing that links the consumption of readily available sugar from food with a higher risk of obesity. Also, there is some concern that fruit juice consumption may displace other more nutritious foods from the diet, increasing the risk of malnutrition. One study published in the journal Pediatrics found that young children drinking more than 360 mls of fruit juice each day were prone to short stature and obesity.

While I do not think that fruit juice should be forbidden for kids, it does seem as though there is good reason for them to consume it with some caution. I recommend a limit of a glass or two each day, and that this be diluted half-and-half with water. This will help to reduce any undesirable effects that might be inflicted by sugary load found in fruit juice. While such drinks may have a healthy image, a closer look reveals some juicy details that some may find quite unpalatable.

Observer Column – 24th August 2003

I was very pleased to see that the World Health Organisation has recently taken a dietary tack, and is urging wide-scale reductions in the amount of sugar added to fast and processed foods. A potential consequence of consuming too much sweet stuff is an excess of the sugar-regulating hormone insulin, which in turn may precipitate a range of unwelcome effects including weight gain, high blood pressure and an increased susceptibility to diabetes. However, conventional dietetic wisdom dictates that not all sugars have the same capacity to cause our body’s chemistry to go awry. Nutritional scientists tell us that fructose, the principle sugar found in fruit, does not inflate levels of sugar or insulin in the system. Its seemingly benign effects mean that fructose has traditionally enjoyed a somewhat sugar-coated reputation.

Fructose’s healthy image (and its relative cheapness) have seen it assume a substantial and growing prominence as an additive in the American diet. An almost inevitable consequence of this is that fructose-sweetened foodstuffs (often in the form of what is known as high fructose corn syrup) are becoming increasingly commonplace on this side of the Atlantic. I see this example of the Americanisation of our diet as a worrying trend. While it is often said that fructose does not upset our internal balance, the reality is that studies have found that it can impair the body’s ability to handle sugar, and can reduce the effectiveness of insulin too. What is more, animal experiments reveal long-term consumption of fructose can indeed lead to elevated levels of both sugar and insulin. Taken as a whole, the science strongly suggests that fructose has diabetes-inducing potential.

The sweet sorrow fructose may inflict on the body does not end there. Studies show that fructose may push up blood levels of blood fats called triglycerides ” believed to be an important risk factor for heart disease. Animal research has also found that fructose feeding can boost blood pressure, an effect that is also likely to increase the risk of the UK’s premium killer. In addition, fructose has been found to lower levels of leptin ” a hormone with appetite-suppressing effects that is believed to play an important part in the regulation of food intake. Its capacity to quell leptin levels may help to explain why feeding with fructose has been found to cause animals to eat more and gain weight [2].

One major hazard of dietary sugars is their capacity to react with protein molecules in the body, a chemical union that is believed to play a major part in the ageing process. Studies show that fructose has a great affinity for protein, a property that gives it further potential to erode our health and well-being. Avoiding foods sweetened with fructose or high fructose corn syrup seems like a sensible precaution, though this may require some label reading. One foodstuff that is rich in fructose (although its natural presence will mean it will generally not be declared on the label) is fruit juice. A half-pint of orange juice will provide the body with about three times as much fructose as a whole orange, and will undoubtedly have lost some healthy properties as a result of the juicing process. I recommend that those in the habit of downing a glass of fruit juice in the morning swap this for a piece of whole fruit. Whether from fruit juice or processed foods, there’s good reason to believe that fructose’s reputation as a preferred from of sugar has turned sour.

References:

1. Faith MS, et al. Fruit Juice Intake Predicts Increased Adiposity Gain in Children From Low-Income Families: Weight Status-by-Environment Interaction. Pediatrics. 118;2006: 2066-2075

2. Elliott SS, et al. Fructose, weight gain and the insulin resistance syndrome. Am Jour Clin Nutr 2002 76(5):911-922

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